Cohorts of 1-3 patients receive KRN5500 at the starting dose over escalating infusion durations. After the longest duration of infusion time is safely reached, cohorts of 3-6 patients receive escalating doses of KRN5500 until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 3 or 2 of 6 patients experience dose-limiting toxicity. Once the MTD is determined, additional patients are accrued to receive treatment with KRN5500 at the recommended phase II dose.